Jack.



HENRY JOHNSON, 0F DETROIT, MICHIGAN.

JACK.

Specification of Letters Patent.

Patented Dec. 31', 1918..

Application tiled-March 8, 1918. Serial No. 221,232.

To all whom t may concern Be it known that I, HENRY JOHNSON, a subject of the King of Sweden, residing at Detroit, in the county of lVayne and State of Michigan, have invented new and usefl Improvements in Jacks, of which the following is a. specification. y

This invention comprehends the provision of a pneumatic jack of a compound nature, wherein the lifting element is subjected to the air pressure at spaced superimposed points in its lifting power, as well as effecting the rapid elevation of said element proportionately with regard to the load to be lifted', and finally providing a double resistance for the object supported upon the jack, the lat-ter possessing maximum strength and durability.

VVhile a general application of the invention is contemplated, it is tended for hoisting vehicle odies or the like, and it embodies among other features a pair of telescopic communicating cylinders, one of which constitutes a support for the jack and the other the lifting element, the latter being'provided with a piston operating within the lowermost cylinder so that when air under pressure is introduced into the cylinders the upper end of the lifting element as well as the piston are subjected to pressure for the purpose above mentioned.

Another important characteristic of the invention resides in providing the upper end of the supporting cylinder with a safety valve adapted to be opened when the lifting element is in full extended position, thus allowing the excess of air pressure to escape through a suitable outlet, should under any circumstances air be forced into the cylinders after the lifting element has been adjusted to its maximum extent.

The nature and advantages of the invention will be readily apparent when the following detailed description is read in connection with the accompanying drawings, the invention residing in the construction, combination and arrangement of parts as claimed.

In the drawing forming a part of this specification, like numerals of reference indicate similar parts in the several views, and wherein Figure 1 is a vertical sectional view length thereby increasi-ng the primarily inthrough the jack showing the lifting element partly adjusted;

Fig. 2 is a similar view showing the lifting element subjected toits maximum height and the safety valve opened;

Fig. 8' is a top plan View;

Fig. 4 is a transverse sectional view taken on the line 4-4 of Fig. 2.

The'jack constructed in accordance with my invention essentially consists of a pair of hollow cylindrical members 10 and 11 respectively, the latter being t-elescopically fitted within the former as illustrated. In use of the jack the cylinder 10 constitutes the li-fting element, while the cylinder 11 constitutes the supporting cylinder, which rests upon the ground or surface. In the further description of the invention these cylinders will be referred to accordingly.

The supporting element 11 is provided with a relatively broad base 12, while the opposite end ofthis element is interiorly threaded for a portion of its length to accommodate the plug 13 which constitutes a closure for the member 11. The plug is provided with a restricted central aperture to slidably receive the piston rod 14, which depends from the upper end of the lifting element 10. vA piston 15 is carried by the lower extremity of the rod 14 and operates within the supporting element 11. The piston 15 may form an integral part of the rod 1t or may be otherwise detaohabh7 associated with the rod in any suitable manner. A leather disk or packing 16 surrounds the piston rod 14 and reposes upon theI plug 13 --in the upper end of the supporting element 11. The packing is slightly upturned as at 17 to snugly engage against the piston rod 14 and the wall of the lifting element '10 to provide a fluid-tight connection between, these parts. A washer 18 also surrounds the piston rod 14 and rests upon the disk 16. Any suitable means may bc employe-d for maintaining thev washer 18 secured to the plug 13. The washer is provided with inner and outer peripheral grooves 19 in each of which is arranged an expansible ring 20. The rings are utilized to hold the disk or packing 16 in effective engagement with the piston rod 14 and the wall of the lifting element 10, the rings exerting a pressure against the upturned portion 17 for this purpose. The piston rod 1t is provided with a longitudinal bore 21 including a .through into the supporting cylinder 11. -A

disk of suitable packing material 24 is arranged against the bottom of the piston land has its peripheral edge downturned as at 25 to effective-ly engage the wall of the cylinder 11 tok prevent the escape of air therefrom. A washer 25 bears against the disk 24 and is provided with a peripheral groove 26 for the reception of an expansible ring 27, whichexerts a pressure against the downturned edge portion of the. packing to maintain the latter against vthe w-all of the cylinder 11. A hollow substantially *V- shaped member has its .stem portion 28 threaded Within the bore 21 of the piston 15 with ,the cross piece or head 29 of said member bearing against the washer 25' to hogld the latter properly positioned with respect to the disk 24. The piston rod 14 passes throughl aV restricted central opening in the top of the lifting element 10 and is provided with a reduced exteriorly threaded portion 30. A yoke 31 which engages the object to be lifted, rests upon the upper end of the lifting element 10 and is provided with an linternal shoulder 32. A suitable. nutv 33is secured to the threaded extremity 30 of the piston rod and is provided with a c shoulder 34 which engages thel shoulder 32 of the yoke thus holding the latter fixed relatively to the lifting element 10 as will l be readily understood. In addition to maintaining the yoke 31 in proper position upon t-heelement 10, the nut 33 also serves to hold the piston rod? 14 operatively associated with said lifting element. The nut 33 is provided with openings35 to accommodate a suitable tool `when it is desired to effect an adjustment of the nut.

--In practice, a/ rubber hose `(not shown) leading from a compressed air tank, or a 'motor operated air pump, (not shown) is coupled to the intake nipple 23 of the lifting element 10, or to the nipple 23 of the I supporting element 11. The nipple has housed therein any Well known form of yvalve which opens inwardly. and herein indicated generally at 36. As air under pressure is introduced into the lifting element 10 or the supporting element 11. a portion of the air enters the bore 21 of l the piston 14 and is obviously' conveyed into the opposite cylinder. As the respective cylinders become filled with air the requisite pressure is exerted agalnst the top of the llifting element 10 and the piston 15 to elekvate the lifting element 10 upon the element The construction defines a jack of a vcompound nature, which in addition to posj pass freely through the port 37 to the atmosphere. When the lifting element 10 has been elevated to the desired extent, the air tube not shown is separated from the nipple 23 thus allowing the valve 3G to close. The air within the lifting element 10y and also within the cylinder' 11 provides a double resistance to the load supported .upon the yoke 31. Manifestly, the invention not only provides a simple compact construction and arrangement of parts, but a jack possessing maximum lifting power, strength and durability.

In carrying out my invention, use is made of a safety valve to prevent injury to the vjack as an entirety, by excessii'e air pressurer` after the lifting element 1() has assumed its full extended position. In this connection a valve casing 39 is fitted Within thc plug 13 and-formed to provide a valve scat 40. A valve 41 normally engages said seat and includes a stem 42 which projects through vthe casing 39 terminating an appreciable distance below the plug 13. A

'- coil spring 43 encircles the projecting por- .n of the stem and has one end bearing hagainst a pin 44 passed transversely through the stem, while the opposite end of the spring contacts the adjacent end of the casing 39, so that the spring operates to maintain they valve normally seated. Now, .when

the lifting element 1() reaches the limit of its adjustment in an upward direction, and air under pressure continues to enter the intake opening 23, the. excessive pressure within the cylinderswould obviousl have a very detrimental effect upon the jack, if it were not for the fact that the piston 15 is forced into engagement with the valve stein 42, thus unseating the valve and permitting this excessive pressure tol pass through the casing 39 to the outlet port 37 of the cylinder 11, Of course, when the piston 15 is moved away from the valve stem the valve is automatically seated under the influence of the spring 43. Vhen it is desired to lower the lifting element 10, it is only necessary to move the valve 36 inwardly to an open position thus allowing the air to escape from both of the cylinders 1() and 11 respectively. Obviously, for the purpose the air passes upwardly from the cylinder 11 through the bore 21 -posed communicating cylinders,

of the piston rod 14 into the cylinder 10.

In this manner the lifting element 10 returns from its adjusted to its normal position gradually, and without any danger to the operator or injury to the object supported upon the jack.

It is also the purpose of the invention to provide a scraper, in the form of an annulus` of leather or other suitable material, which forms a dust proof joint between the lifting and supporting elements and also acts to scrape away dust or. dirt from the inner wall of the lifting element.

In addition, a handle 51 is pivotally secured to the base of the supporting element for convenience of positioning the jack beneath an object.

While it is believed that from the foregoing description the nature and advantages of the invention will be readily apparent, I desire to have it :understood that I do not limit myself to what is herein shown and described, as the same merely constitutes the preferred embodiment of the invention, and that such'changes may be resorted to when desired as fall .within the vscope of what is claimed.

'Having described the invention, what is claimed is 1. In a pneumatic jack, a pair of superimposed communicating cylinders, one of which is slidably mounted upon the other, a valve controlled air inlet in said movable cylinder, a piston carried by said cylinder and operating Within the lowermost cylinder, exhaust located above said plston.

2. In a pneumatic jack, a pair of superimone of said cylindersbeing slidably mounted upon the other, the movable cylinder having a valve controlled air inlet port, a piston rod disposed within the movable cylinder, a piston carried by said rod and operating within the other cylinder, the latter mentioned cylinder having an air exhaust port located above the piston, a yoke mounted upon the movable a p-iston on and said latter cylindenhaving an air cylinder, and nieans common to both the piston rod and said yoke for holding said part fixed relatively to said movable cylinder.

3, In a pneumatic jack, a pair of superimposed cylinders, one being slidably mounted upon the other, said movable cylinder having a valve controlled air inlet port, a piston rod carried by the movable cylinder,

the lower end of said rod operating within the other cylinder, said rod having a longitudinallydisposed bore for establishing communication between said cylinders, and the latter mentioned cylinder having an air exhaust port located above said piston.

4. In a pneumatic jack, a pair of superimposed communicating cylinders, one of said cylinders being slidably mounted uponthe other, said movable cylinder having a valve controlled'air inlet p'ort, the other cylinder having an exhaust port adjacent the upper end thereof, a piston in one of said cylinders, a normally closed release valve carried by the said upper end of the latter mentioned cylinder, and said valve .being opened by means of said piston when the latter reaches the limit of itsadjustment in one direction.

5. In a pneumatic jack, a pair of superimposed communica-ting cylinders, one or said cylinders being slidably mounted upon the other,` said movable cylinder having a valve controlled air inlet port, the other cylinder having an exhaust port adjacent its upper end, a piston in one of said cylinders, a spring pressed release valve carried by the upper end of th'e latter mentioned cylinder, said valve being normally seated and including a stem projecting .within 'said cylinder and terminating in the path of movement of the piston within said cylinder, whereby said valve is opened by the piston when the latter reaches the limit of its adjustment in .an upward direction.

In testimony whereof I affix my signature.

HENRY JOHNSON. 

